Santiago Casilla might not miss much time with a sore right shoulder, but on Saturday, the A’s placed the reliever on the disabled list and called up reinforcements for their overtaxed bullpen.

Chris Bassitt, a former member of Oakland’s rotation, was recalled from Triple-A Nashville and will provide long relief, and Carlos Ramirez, obtained on waivers from Toronto last week, also was called up and potentially will be used in matchup situations against right-handers.

In addition, the team will call up right-hander Frankie Montas on Sunday to start against Arizona, pushing Trevor Cahill’s next start to Monday’s day game. The team wanted to get Cahill an extra day of rest because he’s only two starts removed from a DL stint with a right elbow impingement.

Right-hander Josh Lucas, who made a spot start Thursday, was sent down to make roster room; he would have been unavailable for another day or two. The A’s will have to make another move Sunday to create a spot for Montas.

Manager Bob Melvin said Casilla’s injury is similar to one he had during spring training that responded well to several days off, and he speculated that Casilla might spend only the 10-day minimum on the DL.

Bassitt was 2-2 with a 6.35 ERA and .316 opponent average in eight games, including five starts, with Nashville, and he is 1-2 with an 11.15 ERA in five starts since he was optioned back down. Ramirez worked in one game for Nashville after being claimed May 20 and struck out three in two scoreless innings.

Casilla has a 3.32 ERA in 16 appearances. Opponents are batting .153 against him, sixth lowest among relievers.

Montas, obtained in the Rich Hill-Josh Reddick deal with the Dodgers in 2016, put up a 7.03 ERA in 23 relief outings with Oakland last year, but his ERA in May with Triple-A Nashville is 3.24.

“Talking to our people, Frankie is pitching pretty well right now,” Melvin said. “He’s throwing strikes, he’s had a couple of good outings.”

The A’s other option at Nashville was Kendall Graveman, Oakland’s Opening Day starter. Graveman, sent down to work on his delivery, has allowed four runs in 12 innings in his past two starts, but he started for Nashville on Thursday, so he is not available Sunday.

Susan Slusser has worked at The San Francisco Chronicle since 1996. She has been a member of the Baseball Writers Association of America since 1993 and in 2012 became the only woman to be elected president in the 111 years of the organization. She has written about many other sports for the paper, particularly hockey and, more recently, e-sports.

Susan previously covered the Texas Rangers for the Dallas Morning News, the Orlando Magic for the Orlando Sentinel, and the NBA and other sports for the Sacramento Bee.

Susan is an on-air correspondent for the MLB Network and makes regular appearances on 95.7 FM The Game. Her book about the A’s, 100 Things A's Fans Need to Know and Do Before They Die, came out in 2014 and she and A’s radio announcer Ken Korach are working on a book that will come out in 2019.